1. Field of the Invention
The present invention relates generally to fire retardant compositions and methods, and more particularly to fire retardant compositions suitable for application to flexible substrates. This invention also relates to laminates comprising such fire retardant compositions and methods for making them.
2. Description of Related Art
Fabrics, leather, synthetic leather, films, foils, paper, and other articles used in applications for aircraft, automotive, hotel, casino and marine as well as other industries are typically required by international governmental bodies to meet one or more often rigorous flammability or fire retardant tests such as FAR 25.853 (a), Appendix F; MVSS 302; NFPA 701; Nord Arch; BS 5852 and others. That is, the material being used inherently must be flame retardant, even before it is manufactured into an article. Many upholstery, covering or other materials inherently are flammable, at least to some extent, and are therefore not capable of passing flammability tests. Accordingly, many materials must be treated in some way with fire retardant chemicals, often in high quantities, in order to meet requirements that they otherwise could not meet.
Fire retardancy can be imparted to materials in several different ways. For example, resinous materials can be reformulated to include one or more fire retardant materials within the structure of the material itself. Reformulation only is appropriate in some situations, and is inapplicable to natural materials such as leather or cotton. Alternately, it is possible to saturate, impregnate or spray coat a material with a liquid fire retardant, and then flash off the liquid or solvent to leave the residual fire retardant. Saturation methods, however, present several disadvantages. For example, with nonporous materials, there might be insufficient uptake of active chemical to provide the desired level of fire retardancy. Porous materials, while being able to absorb the active chemical, could be stiffened by the chemical.
For fabrics where a specific texture is desired for performance or aesthetics (such as a natural or synthetic suede, velour, etc.) the saturant method of incorporating the fire retardant chemical can in some circumstances severely compromise or destroy the surface texture. In addition, impregnation or spray coating processes often do not apply the fire retardant chemicals evenly over the entire surface material being treated, resulting in some areas being overly treated, while other areas have little or no applied fire retardant. This is particularly prevalent in spray coating processes which often are done manually. There can be other drawbacks due to the fire retardant material itself. For example, some fire retardant chemicals that are dissolved in water or a solvent vehicle can become redissolved by water or solvent and hence, the fire retardant properties are not durable. In addition, water-soluble fire retardant chemicals can be leached out during use, thereby resulting in loss of flame retardant properties. Such leaching can also cause detrimental changes in the appearance of the treated article, such as by "chalking" or "blooming" due to migration of chemical to the surface or face either initially or over time. In fact, some flammability tests such as Nord Arch and BS 5852 require testing of subject material after it has been washed. Thus, if fire retardancy is imparted by saturation, there always is the chance that the material will not meet the test specification after it has been washed or otherwise exposed to liquid.
Moreover, there are environmental and practical concerns associated with the use of many solvents or fire retardant chemicals, particularly when coatings are sprayed on. Thus, many impregnating or coating processes have to be conducted under strict regulations to avoid exposure of harmful materials to the operators. Further, setting up a spray coating process line can be time consuming and expensive. Thus, it is impractical to do so to coat only a small amount fabric or other substrate. This practically limits the use of non-fire retardant fabrics where fire retardancy is required.
A resin can be included with the fire retardant and solvent to act as a binder. However, the use of a resin binder can be very detrimental to the "hand" or "drape" of a material into which it has been impregnated. ("Hand" and "drape" are terms commonly used in the fabric industry to describe certain qualitative properties relating to the feel of the material.) This is because the binder will bind or tie individual fibers of the material together, thus turning a fabric that is soft and supple into something resembling paper in stiffness. For example, it has been proposed to heat seal an abrasion resistant polyurethane to the face of a fabric in U.S. Pat. No. 4,284,682. This process may work in certain applications, but not in cases, for example, where the outer surface of the material should not be altered, and where it is desirable to preserve the hand and drape of the material being treated.
In addition, it has been proposed in U.S. Pat. No. 4,806,185 to employ a fire barrier material between a decorative outer upholstery fabric and a filler material (such as a cushion). The fire barrier material of this patent is a woven or nonwoven material made of coated fibrous substances such as glass fibers, carbon fibers, polyaramid, polybenzimidazole, polymeta-phenylene diamine isophthalate or combinations thereof. There is also provided a coating of latex and a heat conductive metal such as aluminum, copper or nickel. Such materials are generally prohibitively bulky such that they cannot be applied to fabrics for which thickness is critical. Further, when applied to many fabrics, such fire retardant barriers will tend to substantially alter the "hand" of the underlying fabric.
The underlying problem therefore, that exists in the art, relates to how to provide fire retardant to materials such as fabrics without deteriorating their properties (surface texture, hand, drape and the like). Methods of the prior art inherently exhibit leaching of solvents and uneven and/or insufficient application (when spray coating is employed) as well as almost always involve an undesirable stiffening of the underlying fabric. In accordance with the present invention, wherein a cured film including a fire retardant is applied to a substrate, the disadvantages associated with spray coating as well as the undesirable stiffening of the substrate are eliminated.